Prospective Multiple Antenna Technologies for Beyond 5G

TL;DR

This paper surveys emerging multiple antenna technologies like cell-free massive MIMO, beamspace massive MIMO, and intelligent reflecting surfaces, which are crucial for meeting the demanding requirements of beyond 5G networks.

Contribution

It introduces and discusses three novel antenna technologies and outlines future research directions for beyond 5G communication systems.

Findings

Overview of cell-free massive MIMO, beamspace massive MIMO, and intelligent reflecting surfaces.

Recent technical progress in these technologies.

Identification of future research challenges and directions.

Abstract

Multiple antenna technologies have attracted large research interest for several decades and have gradually made their way into mainstream communication systems. Two main benefits are adaptive beamforming gains and spatial multiplexing, leading to high data rates per user and per cell, especially when large antenna arrays are used. Now that multiple antenna technology has become a key component of the fifth-generation (5G) networks, it is time for the research community to look for new multiple antenna applications to meet the immensely higher data rate, reliability, and traffic demands in the beyond 5G era. We need radically new approaches to achieve orders-of-magnitude improvements in these metrics and this will be connected to large technical challenges, many of which are yet to be identified. In this survey paper, we present a survey of three new multiple antenna related research directions that might play a key role in beyond 5G networks: Cell-free massive multiple-input multiple-output (MIMO), beamspace massive MIMO, and intelligent reflecting surfaces. More specifically, the fundamental motivation and key characteristics of these new technologies are introduced. Recent technical progress is also presented. Finally, we provide a list of other prospective future research directions.